Water swelling pressure sensitive adhesives based on polyethylene oxide (PEO) are known and are generally useful in any of a variety of articles including medical articles. The use of such materials in medical articles includes wound dressings, wound packings, contact lenses, intraocular lenses, adhesives for biological tissues, adhesion preventing materials, adsorbents for blood purification, base materials for releasing pharmacologic agents, biomedical electrodes, and the like. Materials used in dentistry may also incorporate such pressure sensitive adhesives for dental moldings or impressions, dental adhesives, restoratives, coatings, composites, sealants and the like. As used herein, “medical” applications are intended to encompass dental applications, including dental adhesives, restoratives, coatings, composites, sealants, etc. Because water swelling polymer gels have compositions and mechanical properties similar to those of biological tissues, such gels may be applied in a wide variety of fields in the future.
A common method for imparting a desired balance (tack) between cohesiveness and adhesion in pressure sensitive adhesive materials has been by the use of high-energy radiation (e.g., ultraviolet) to assist in randomly crosslinking the PEO to a predetermined cross-link density. An alternate method involves the free radical cure of a PEO-based precursor end capped with ethylenic unsaturation. This alternate method utilizes a procedure for building the molecular weight of the precursor to a desired level from low molecular weight polyethylene glycol diamines and diisocyanates through multiple condensation reactions and end capping with ethylenically unsaturated moieties. While effective, this alternate method requires precise control of the chain extension reactions which can be labor-intensive and time-consuming.
In the preparation of the foregoing precursors, PEO material of a desired molecular weight is first endcapped with reactive ethylenic unsaturation. Suitable end groups might include any of a variety of materials. Methacrylate end groups may be desired where the final adhesive material is to be used in medical applications. Methacrylates are generally easy to make and have a low potential to cause skin irritation.
It is desirable to provide adhesive materials, such as pressure sensitive adhesive hydrogels, from oligomeric precursors end capped with ethylenic unsaturation. It is also desirable to provide the foregoing adhesive materials in a more efficient and cost effective manner than has previously been provided in the art. It is desirable to provide the foregoing oligomeric precursor as a polyether moiety endcapped with ethylenic unsaturation and to further provide the foregoing adhesive hydrogels for use in medical applications, if desired.